Where to get Xbox live Gold membership?

New to Xbox. Need your help.

Bought my son an Xbox 360 to play minecraft and garden warfare online.
One month trial is finished. What can I do?

1. Must he get a Xbox Gold subscription to continue to play the game?

2. The in app purchase offer is $79.95 + free games download. Read other posts in ozbargain - that you can get 12+1 months for approx US$42, or from ozgameshop for lower price. But a bit scare after reading others received used code after paying. What would you do?

3. Does it need a headset to talk to other kids when playing in minecraft or garden warfare? I bought a 3.5mm to 2.5mm stereo converter, so to plug an iphone/normal earphone to the Xbox controller (learnt from Youtube) - sadly does not work. Either can hear or talk, not talk and listen at the same time. Now I try to turn on the Kinect chat and see if it works.

Wiz kids - please help.